CN102288113B - Optical position measuring instrument - Google Patents
Optical position measuring instrument Download PDFInfo
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- CN102288113B CN102288113B CN201110131850.1A CN201110131850A CN102288113B CN 102288113 B CN102288113 B CN 102288113B CN 201110131850 A CN201110131850 A CN 201110131850A CN 102288113 B CN102288113 B CN 102288113B
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- front corrector
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
- G01D5/3473—Circular or rotary encoders
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/36—Forming the light into pulses
- G01D5/38—Forming the light into pulses by diffraction gratings
Abstract
The present invention relates to a kind of optical position measuring instrument, it is for detecting the relative position of scanning element and metering device; Scanning element and metering device can be arranged along bending direction of measurement with moving relative to each other.Scanning element has at least one reflector element and detector cells, and wherein reflector element is made up of the first wave-front corrector, beam direction reverser and the second wave-front corrector.Reflector element was arranged and/or is constructed so that before part beam finally arrives detector cells in scanning element, beam is first through the first combination be made up of metering device and the first wave-front corrector, then carry out part beam by beam direction reverser and return reflection in metering device direction, and part beam is then through the second combination be made up of metering device and the second wave-front corrector.
Description
Technical field
The present invention relates to a kind of optical position measuring instrument.
Background technology
For detecting metering device and scanning element along the optical position measuring instrument of the relative motion in flexural measurement direction when, two kinds of fundamental types should be distinguished:
A) there is the optical position measuring instrument of the metering device of the radial calibration form be arranged on index plate;
B) there is the optical position measuring instrument of the metering device of the cylinder calibration form be arranged on index sleeve.
Beginning mention optical position measuring instrument comprise there is meticulous radial calibration index plate as metering device, when this optical position measuring instrument, the location tolerance of metering device is normally minimum compared with scanning element.This is because violent signal declines, it is little radial direction between radial calibration and specified installation site that this signal declines, tangential or lengthwise position deviation just because the thing followed causes participating in the wavefront distortion in the part beam that signal generates, this wavefront distortion causes interference to superpose.At this, the grating constant changed diametrically of radial calibration causes strong wavefront distortion.This means, by the wavefront of the part beam of radial calibration diffraction, partly be there is the remarkable deviation relative to plane wave front.
Also occur similar problem when second describes the optical position measuring instrument of type, wherein metering device is disposed in the periphery of rotating cylinder or rotating cylindrical as so-called cylinder calibration.At this, bending cylinder calibration causes the distortion for generating the wavefront in the part beam of signal equally.
Such wavefront distortion also just occurs at the ideal mounting position place of metering device, and is called as nominal wavefront distortion later.The additional wavefront distortion caused by tolerance is produced when imperfect installation site.Therefore, the signal that the beginning in generated position signalling is mentioned fallen suddenly bearing prime responsibility for generating the different wavefront distortion that occur in the part beam of signal.Result is the signal quality of the obvious variation of such optical position measuring instrument.
In addition, in the retroreflector being known to use prism form for detecting in relative to the high-resolution optical position measuring instrument of the linear push shifting movement of metering device and scanning element; Such as EP387520A2 can be consulted to this.In the scanning optical path proposed wherein, the collimated beam of lasing light emitter is diffracted to the part beam of the+1 and the-1 order of diffraction at the striated pattern place of metering device.Then, this part beam deflects on the striated pattern of metering device again by means of the retroreflector of one or more prism form.After further diffraction occurs at metering device place, two part beams interfere at lap position place.By using described one or more retroreflector being configured to prism, ensure when metering device tilts arbitrarily relative to scanning element, two part beams also keep its direction after metering device place re-diffraction.So, do not interfere the wavetilt of part beam.In this way, when the large beam cross-section of the meticulousst calibration cycle of metering device and the position of large scanning plane, i.e. metering device, additionally also large location tolerance can be realized.But the superperformance of such optical position measuring instrument substantially based on, the wavefront of part beam after the striated pattern place diffraction of metering device and all keep little as far as possible after the reflection of retroreflector place.Thus, wavetilt is compensated by the retroreflector being used in an ideal way due to the inclination of metering device.
If also use now high-resolution optical position measurement apparatus detect metering device and scanning element along bending direction of measurement relative motion, namely use the system with radial grating calibration and cylinder calibration in conjunction with retroreflector, then cause certain problem.At US5,442, carry out analyzing to these problems in 172 and proposed the solution of the imagination.Therefore, wavefront distortion will be reduced to the adverse effect of signal quality according to the document by proposing desirable reflector element.This reflector element comprises spherical mirror and is arranged in the combination of the roof prism in the focal plane of lens.But drawing by analyzing more accurately proposed scanning optics, causing when metering device and scanning element misalignment more and more significant signal to decline.In addition, when proposed desirable retroreflector unit, beam focus is in the ridge seamed edge place of roof prism, and therefore this roof prism can not produce any error in this region.In this region, do not allow to there is a bit unevenness, such as, be mingled with, pollute or space.Due to the high manufacture requirements to such parts, this roof prism is extremely expensive.
Summary of the invention
Task of the present invention is, illustrate a kind of for large location tolerance to detect scanning element and can with the high-resolution optical position measurement apparatus of flexural measurement direction to the relative motion of the metering device of its movement.
According to the present invention, this task is solved by the optical position measuring instrument of the feature with claim 1.
Favourable embodiment according to optical position measuring instrument of the present invention draws from the measure of dependent claims.
Optical position measuring instrument according to the present invention comprises scanning element and metering device, and wherein scanning element and metering device can move relative to each other along bending direction of measurement.By position measurement apparatus according to the present invention, the relative position of scanning element and metering device can be detected.Scanning element side is provided with at least one reflector element and detector cells.Reflector element is made up of the first wave-front corrector, beam direction reverser and the second wave-front corrector.Reflector element was arranged and/or is constructed so that before beam finally arrives detector cells in scanning element, beam is first through the first combination be made up of metering device and the first wave-front corrector, then carry out part beam by beam direction reverser and return reflection in metering device direction, and part beam is then through the second combination be made up of metering device and the second wave-front corrector.Ensured by reflector element, the wavefront distortion of the part beam that the first diffraction due to metering device place produces is converted into such wavefront distortion, and namely this wavefront distortion compensates the wavefront distortion caused when the second diffraction occurs at metering device place.
To become have the collimating part beam of flat wavefront from metering device and the wave-front conversion of the first combination outgoing of the first wave-front corrector advantageous by the first wave-front corrector.By the second wave-front corrector by becoming to have the collimating part beam of flat wavefront from metering device and the wave-front conversion of the second combination outgoing of the second wave-front corrector, make to cause the wavefront of the part beam superposed identical at superposed positions place after second diffraction at metering device place.
Can specify at this: the first combination of metering device and the first wave-front corrector is disposed on beam propagation direction with the order of metering device-the first wave-front corrector, the second combination of metering device and the second wave-front corrector is disposed on beam propagation direction with the order of the second wave-front corrector-metering device.
Be alternative in this, can specify: the first combination of metering device and the first wave-front corrector is disposed on beam propagation direction with the order of the first wave-front corrector-metering device, the second combination of metering device and the second wave-front corrector is disposed on beam propagation direction with the order of metering device-the second wave-front corrector.
Preferably, beam direction reverser is constructed to make to reverse the beam direction of the part beam aspect reflected from it to carry out in 2 orthogonal directions.
In a possible embodiment, beam direction reverser can be configured to triple spiegel or prism.
In addition, beam direction reverser can comprise the combination of lens and catoptron.
It is possible that the lens of wave-front corrector and/or beam direction reverser are configured to refraction optical element.
Wave-front corrector can be configured to diffraction optical element.
It is additionally possible that wave-front corrector is become diffraction optical element with the lens arrangement of beam direction reverser.
In addition can specify: diffraction optics composition element wave-front corrector being configured to respectively raster form, this raster in addition to the part beam fallen on it have in following Additional optical function one of at least:
The effect of-deflection optical
-optical beam splitting or synergy
-to the optical focus function on catoptron.
At this, catoptron and diffraction optical element can be arranged in the opposite side of lens scan plate.
In another embodiment, metering device is configured to the radial calibration on the graduated disk that rotates around turning axle and is arranged as around turning axle concentric.
Be alternative in this place can specify: metering device is configured to the cylinder calibration on the periphery of rotary index cylinder, and wherein turning axle overlaps with the major axis of index sleeve.
At this advantageously, the optical element in scanning element is constructed and is arranged so that the beam launched from light source is fallen a calibration with the angle being not equal to 90 °.
Therefore, according to the scanning optics of the optical position measuring instrument of the present invention special structure based on reflector element.This ensures: the part beam of measured apparatus diffraction is reflected back toward metering device again, makes described part beam have equal wavefront when superposing.Therefore, the maximum interference contrast when interference signal generates is ensured.All be guaranteed when this ideal mounting position at metering device and the deviation caused by tolerance little with it.Therefore, by the scanning optics of optical position measuring instrument according to the present invention, nominal wavefront distortion and the wavefront distortion caused by tolerance are all reliably corrected.Can signal be avoided suddenly to fall when the relative aligning of metering device with the possible non-optimal of surface sweeping unit thus, that is ensure desired location tolerance.
In addition, the obvious simplification of scanning optics can be realized by measure according to the present invention, that is also can manufacture scanning optics with low cost.
In addition it should be mentioned that wavefront distortion increased along with the calibration cycle diminished when the position measurement apparatus according to prior art.For this reason, when installation and operation tolerance given in advance and reasonably scanning field intensity, the resolution of calibration cycle of metering device and thus position measurement apparatus is restricted.By optical position measuring instrument according to the present invention, also can use the less calibration cycle in metering device side now, that is, resolution can obviously increase.
Accompanying drawing explanation
From drawing additional advantage of the present invention and details to the description of embodiment with reference to the accompanying drawings below.
Fig. 1 a-1e respectively illustrates the difference diagram for setting forth for obtaining the wavefront distortion occurred when retroeflection in the part beam of signal;
Fig. 2,3a, 3b show a part for the scanning optical path of the first embodiment according to optical position measuring instrument of the present invention respectively with different views;
Fig. 4 shows the vertical view of the wave-front corrector of the first embodiment according to optical position measuring instrument of the present invention;
Fig. 5 shows another diagram of the scanning optical path of the first embodiment according to optical position measuring instrument of the present invention;
Fig. 6,7a, 7b show a part for the scanning optical path of the second embodiment according to optical position measuring instrument of the present invention respectively with different views;
Fig. 8 shows the schematic diagram of the wave-front corrector of the second embodiment according to optical position measuring instrument of the present invention;
Fig. 9,10a, 10b show a part for the scanning optical path of the 3rd embodiment according to optical position measuring instrument of the present invention respectively with different views;
Figure 11 a, 11b show a part for the scanning optical path of the modification of the 3rd embodiment according to optical position measuring instrument of the present invention respectively with different views;
Figure 12 shows the schematic diagram of the grating calibration of the embodiment according to optical position measuring instrument of the present invention from Figure 11 a, 11b;
Figure 13,14a, 14b show a part for the scanning optical path of the 4th embodiment according to optical position measuring instrument of the present invention respectively with different views;
Figure 15 shows the schematic diagram of the scanning optical path of the first flexible program of the 5th embodiment according to optical position measuring instrument of the present invention;
Figure 16 shows the schematic diagram of the scanning optical path of the second flexible program of the 5th embodiment according to optical position measuring instrument of the present invention;
Figure 17 shows the schematic diagram of the scanning optical path of the 3rd flexible program of the 5th embodiment according to optical position measuring instrument of the present invention;
Figure 18 shows the different geometry associativities of the flexible program from Figure 17;
Figure 19,20a, 20b show a part for the scanning optical path of the 6th embodiment according to optical position measuring instrument of the present invention respectively with different views.
Embodiment
Before detailed description is according to the different embodiments of optical position measuring instrument of the present invention, first set forth about the problem for obtaining the wavefront distortion occurred when retroeflection in the part beam of signal according to Fig. 1 a-1c.Describe according to solution of the present invention according to Fig. 1 d and 1e.
Fig. 1 a schematically shows following ideal situation: wherein participate in the collimating part beam S of signal acquisition for two
in1, S
in2there is smooth wavefront W respectively
in1, W
in2, described collimating part beam S
in1, S
in2the direction of reflector element R being configured to prism is propagated.These part beams S
in1, S
in2reversed by reflector element R in the direction of propagation and wavefront, and then as again there is flat wavefront W
out1, W
out2part beam S
out1, S
out2anti-parallel return with incident direction.
As started elaboration, when interested optical position measuring instrument and due to radial calibration and cylinder calibration form for obtaining the bending metering device of signal and the possible wrong installation due to metering device, participate in the part beam S of signal acquisitions at two
in1, S
in2the middle uneven wavefront W that there is distortion
in1, W
in2.This situation has been shown in Fig. 1 b.When by the retroeflection of retroeflection unit, uneven wavefront is no longer reversed now, and this is as can be seen from Fig. 1 b.That is, after retroeflection, leave the wavefront being viewed as protrusion (recessed) from the direction of propagation.Therefore, at the part beam S of outgoing
out1, S
out2wavefront W
out1, W
out2in leave significant distortion.Therefore next-not shown-by these part beams S
out1, S
out2when superposition, only produce very little interference constant; Less desirable result is the very little signal intensity in generated position signalling.
And it is desirable that following reflector element R ': it is to one or more incident portion beam S
inhave optical effect, this as illustrated in figure 1 c.Therefore, reflector element R ' will reverse incident portion beam S
inthe wavefront W of any random variation
in.Especially incident portion beam S
inbeam direction will be reversed, and do not change beam spot, incident portion beam again returned as can be seen after retroeflection.
Such ideal reflector unit is called as phase conjugation element, and only can utilize the device of nonlinear optics to realize, and this is unpractical due to other shortcomings in optical position measuring instrument.
Therefore, propose in Fig. 1 d and 1e according to the present invention with the solution shown in high-level schematic mode.At this, Fig. 1 d shows transmitter unit 2000 constructed according to the invention when the ideal of metering device 1000 is installed to from the radial calibration of metering device 1000(or cylinder calibration) incide part beam S on it
inand wavefront W
inoptical effect.Fig. 1 e shows the corresponding situation when metering device 1000 of imperfect installation.
According to Fig. 1 d, incident portion beam S
inwavefront W
inthe wavefront W from otherwise flat is experienced when the bending metering device 1000 being configured to radial calibration or cylinder calibration is in the first diffraction
into distortion or bending wavefront W
in' distortion.Then, corresponding part beam S
in' propagate on the direction of reflector element 2000 constructed according to the invention, reflector element 2000 comprises wave-front corrector 2100, beam direction reverser 2300 and the second wave-front corrector 2200 in principle.For the sake of simplicity, in Fig. 1 d, two wave-front correctors 2100,2200 are shown for unique optical device, to this, two devices separated usually are set in the concrete embodiment of optical position measuring instrument according to the present invention.
By the first wave-front corrector 2100, first by inciding it has W before deformation wave
in' part beam S
in' convert to there is flat wavefront W
in' ' part beam S
in' '.Then, part beam S
in' ' arriving beam direction reverser 2300, this beam direction reverser 2300 will incide the part beam S on it
in' ' retroeflection become there is flat wavefront W
outemission parts beam S
out, namely reflex in incident direction.
Then, this part beam S
outthrough the second wave-front corrector 2200, this second wave-front corrector 2200 will have flat wavefront W
outincident portion beam S
outconvert to and there is W before defined deformation wave
out' part beam S
out'.Undertaken the wavefront distortion occurred at metering device 1000 place that next this wavefront distortion is carrying out is compensated at this by the wavefront distortion that the second wave-front corrector 2200 produces.Therefore, after second diffraction at metering device 2000 place, there is flat wavefront W
out' ' part beam S
out' ' continue to propagate.With it similarly, reflector element 2000 acts on another unshowned part beam, makes after second diffraction at metering device 1000 place, can finally make two part wave beams with flat wavefront be interfered superposition.
For this reason, Fig. 1 e shows reflector element 200 similar effect mechanism in the case where there: wherein metering device 1000 is not desirable installation, makes also to exist except nominal wavefront distortion the additional wavefront distortion caused by tolerance that subwave for generating signal is intrafascicular.This additional wavefront distortion in Fig. 1 e by part wave beam S
in' the wavefront W of inclination after first diffraction at metering device 1000 place
in' represent.When passing first wave-front corrector 2100, part wave beam S
in' the wavefront W of distortion
in' be converted into flat wavefront W
in' ', then, part wave beam S
in' ' by beam direction reverser 2300 retroeflection.Then, there is wavefront W
outthe part beam S of retroeflection
outarrive the second wave-front corrector 2200.Then, the second wave-front corrector 2200 is with defined mode conversion fraction beam S again
out' incident wavefront W
out', make that there is corresponding deformation wavefront W
out' part beam S
out' continue to propagate on the direction of metering device 1000.Due to the wavelength distortion defined by the second wave-front corrector 2200, after second diffraction at metering device place, final generation has flat wavefront W
out' ' emission parts beam S
out' ', this emission parts beam S
out' ' again can interfere with another unshowned part beam and superpose.
Reflector element 2000 shown in Fig. 1 e only just provides emission parts beam S when the wavefront distortion caused by tolerance occurs as just wavetilt and do not occur as the addition bend of wavefront
out' ' smooth wavefront.In this, the reflector element 2000 from Fig. 1 e is distinguished mutually with the reflector element R ' from Fig. 1 c.But in practice, the major part of the wavefront distortion caused by tolerance is the inclination of wavefront, the reflector element 2000 constructed according to the invention from Fig. 1 e is made to demonstrate the optical effect especially expected.
Based on the principle set forth and consideration, be described below now the multiple specific embodiments according to optical position measuring instrument of the present invention above.
first embodiment
The first embodiment according to optical position measuring instrument of the present invention is set forth below according to Fig. 2-5.
First the scanning optical path of the principle of this embodiment is described by means of Fig. 2,3a and 3b.Fig. 2 shows the radial view of respective optical position measurement apparatus in y-z plane; Being oriented to perpendicular to this plane of (bending) direction of measurement.Fig. 3 a and 3b shows the tangential section figure of optical position measuring instrument along the section line AA ' shown in Fig. 2 and BB '.
Shown optical position measuring instrument comprises scanning element 20 and can along flexural measurement direction x to the metering device 10 of its movement.In this case, metering device 10 is configured to the radial calibration that is arranged on graduated disk 11.Graduated disk 11, around turning axle RA, is furnished with metering device 10 and radial calibration around turning axle.
The accurate position signalling of height of the rotary motion about scanning element 20 and metering device 10 is generated by the optical scanning of metering device 10.At this, scanning element 20 and metering device 10 are such as connected with-unshowned-machine part of rotating around turning axle RA relative to one another.The position signalling generated by means of device according to the present invention is fed to-unshowned equally-follow electronic installation, this follows electronic installation such as controls corresponding machine part location by it.
Metering device 10 is configured to reflect calibration in a known manner, and this reflection calibration has the fan-shaped long and narrow indexing structure with reflection characteristic alternately of periodic arrangement in the radial direction of turning axle RA.The typical calibration cycle of suitable metering device 10 is about 1-4 μm.
The scanning element 20 of static arrangement comprises a series of optical element in this example embodiment, and each function of described optical element will be set forth with the description of the scanning optical path offseting relevant position signalling being used for generating below.
First the linear polarization beam S launched from light source 21 is collimated by collimating optics 22, and the radial calibration of graduated disk 11 arriving metering device 10 and can move around turning axle RA.The laser diode of the radiation of emission wavelength lambda=780 μm such as can be used as light source.
It should be pointed out that and need not directly be arranged in scanning element in principle according to the light source 21 in optical position measuring instrument of the present invention; Be alternative in shown flexible program, also can specify: by this light source arrangement outside and flow to scanning element by the radiation that suitable optical waveguide is launched.
Generate two part beams TS1a, TS2a by the diffraction of the+1 and the-1 order of diffraction produced on metering device 10, described part beam is reflected back toward with the direction of scanning element 20.These part beams TS1a, TS2a have nominal wavefront distortion due to the structure of metering device 10 along bending line and may have due to the imperfect installation of metering device 10 wavefront distortion caused by tolerance.
In scanning element 20, part beam TS1a, TS2a arrive first wave-front corrector 24.1a, 24.2a, and described wave-front corrector is arranged in the side of scanning element.By first wave-front corrector 24.1a, 24.2a, be corrected before the deformation wave of part beam TS1a, TS2a.Then, part beam TS1a, the TS2a with the collimation of flat wavefront continue to propagate on the direction of beam direction reverser 26.1,26.2.Beam direction reverser 26.1,26.2 is configured to prism in this embodiment, and incident portion beam TS1a, TS2a are reflected back the direction of metering device 10 by this prism as emission parts beam TS1b, TS2b.At this, diametrically, namely given y direction misplaces, this can be as seen from Figure 2 for part beam TS1b, TS2b.Then, two part beams TS1b, TS2b are through λ/4 plate 25.1,25.2, and by λ/4 plate 25.1,25.2, part beam TS1b, TS2b of two original linear polarizations are converted into left/right circularly polarized part beam TS1b, TS2b.Then, part beam TS1b, TS2b arrive two wave-front correctors 24.1b, 24.2b.The wavefront of these distortions of two part beams TS1b, TS2b represents: after second diffraction at metering device 10 place, superposes at superposed positions place to that two part beams TS1b, TS2b in this case collimate and collinearity.
Then, the detection of phase shifted position signal is carried out from the centering of overlapping portion beam TS1b, TS2b.For this reason, two part beams TS1b, TS2b propagate collimatedly after second diffraction at metering device 10 place on the direction of scanning element 20, and there, described part beam is fallen on beam-splitting optical grating 27.Two incident overlapping portion beam TS1b, TS2b are beamed into three other part beams pair by beam-splitting optical grating 27, described other part beam is propagated on the direction of detecting unit, and arrives the polarizer 28.1-28.3 with different polarization directions arranged with different spaces direction.Finally by the detecting element 29.1-29.3 be arranged in after polarizer 28.1-28.3, carry out the detection of phase shifted position signal; At this, produce the detection of the position signalling of three phase shifts 120 ° in this example.Therefore, in this embodiment, detector cells also comprises polarizer 28.1-28.3 and beam-splitting optical grating 27 except detector cells 29.1-29.3.
According to above to the description of scanning optical path, reflector element used according to the invention, described reflector element comprises first and second wave-front corrector 24.1a, 24.1b, 24.2a, 24.2b respectively and arranges beam direction reverser 26.1,26.2 in-between.Described reflector element and corresponding parts thereof to having radiant section beam TS1a, TS2a and TS1b of distorted wavefront, TS2b applies the optical effect that defines.Ensured by corresponding optical effect: the variation that can not be caused signal quality by the wavefront distortion existing in part beam TS1a, TS2a and the TS1b for generating signal, TS2b.
Therefore, the collimating part beam with flat wavefront is transformed into by first wave-front corrector 24.1a, 24.2a by before the deformation wave of part beam TS1a, TS2a of falling on it; Carried out the distortion of the flat wavefront of part beam TS1b, TS2b of falling on it by second wave-front corrector 24.1b, 24.2b, make the wavefront of part beam TS1b, TS2b that superposes be identical at superposed positions place after second diffraction at metering device 10 place.
In addition, the beam direction reverser 26.1,26.2 used is constructed to make the beam direction reverse at part beam TS1a, TS2a of reflecting from it carry out in both the tangential and radial directions, namely carry out in given y and the x direction of orthogonal orientation in this example.
Therefore, ensure by constructing reflector element in this wise: because the possible wavefront distortion in part beam TS1a, TS2a that first diffraction at metering device 10 place produces is converted into wavefront distortion in part beam TS1b, TS2b, described wavefront distortion compensates the wavefront distortion that the second diffraction due to metering device 10 place causes.
As the beam direction reverser 26.1,26.2 with retroreflection optical effect, prism is set in the reflector element of the present embodiment; For this reason, alternately such as also prism can be used in these positions.
In the first shown embodiment, wave-front corrector 24.1a, 24.1b, 24.2a, 24.2b are configured to the diffraction optical element of raster form.To this, set forth other details according to Fig. 4, Fig. 4 shows the vertical view with the scanning board 23 arranging superincumbent four wave-front correctors 24.1a, 24.1b, 24.2a, 24.2b.
Be similar to likely by good, wave-front corrector 24.1a, 24.1b, 24.2a, 24.2b are configured to the radial scan grating with the radial metering device 10 on graduated disk 11 with the identical calibration cycle, at this, wave-front corrector 24.1a, 24.1b of being configured to radial scan grating on scanning board 23 are with the dislocation separation delta x=-x that staggers abreast on graduated disk 11
lform be arranged to relative with the metering device 10 being configured to radial calibration.At this, dislocation separation delta x represents that the Central places of metering device 10 is in the spacing determined on direction of measurement x of the calibration bar in beam and the gratings strips parallel with it of wave-front corrector 24.1a, 24.1b.And wave-front corrector 24.2a, 24.2b are arranged to the dislocation separation delta x=+x that staggers
l.Required dislocation spacing
according to equation 1 by the radial grating on graduated disk 11 at centre scan radius R
athe beam deflection be on the height of scanning board 23 is determined:
(equation 1)
Wherein:
Effective scanning spacing between D:=metering device and wave-front corrector
R
a:=centre scan radius
λ: the wavelength of=light source
The bar number of the metering device of N:=on graduated disk.
The diffraction optical element that being used on scanning board 23 and corresponding radial scan grating constructs wave-front corrector 24.1a, 24.1b, 24.2a, 24.2b is preferably implemented to phase structure.In simple flexible program, such as, the phase structure with 180 ° of phase depth and the local brace width equal with localized voids width is set.At this, alternately also use the phase structure broken.By this phase structure, also can suppress the unwanted order of diffraction, the further raising of the signal intensity in produced position signalling can be realized thus.
Except optical function discussed up to now, wave-front corrector 24.1a, 24.1b, 24.2a, 24.2b of the present embodiment also have other optical effect.Therefore, described wave-front corrector also has central optical deflecting action, makes to fall part beam TS1a, TS2a or TS1b on it, TS2b is deflected to parallel with optical axis OA.Therefore, the diffraction optics composition element of raster form is also discussed with reference to wave-front corrector below.
As can be seen from the view in Fig. 4 and Fig. 5, part beam TS1a or TS2a staggers slightly to interior in the x direction relative to part beam TS1b or TS2b respectively on the height of scanning board 23.This dislocation ensures: when grating constant different diametrically and deflection angle in local is also different, the same position of part beam TS1b and TS2b on metering device 10, namely meets at superposed positions place and superposes when not having beam to misplace thus.Corresponding optimal location (the X of the prism for this reason arranged in beam direction reverser 26.1,26.2 or the present embodiment
p1, X
p1) and (X
p2, X
p2) draw according to lower relation of plane 2.1-2.3:
(equation 2.1)
(equation 2.2)
(equation 2.3).
These relation 2.1-2.3 set up following coordinate system: the center of this coordinate system is in the center of graduated disk 11, and the x-axis of this coordinate system is consistent with direction of measurement x, and the z-axis of this coordinate system to be oriented to metering device 10 orthogonal.This coordinate system also uses in other description process.
Therefore, in the x plane of Fig. 4, the tip being configured to the beam direction reverser 26.1,26.2 of prism is symmetrical between part beam TS1a and TS1b or TS2a and TS2b on wave-front corrector 24.1a, 24.1b, 24.2a, 24.2b.
The wavefront of beam TS1a and TS2a in first wave-front corrector 24.2a, 24.2b position numerically or by so-called ray-tracing scheme or by wave traveling can be determined by known mode.If make the raster phase of wave-front corrector 24.1a or 24.2a equal these wavefront, then can calculate more preferably diffraction structure.The axial scan optical grating construction drawing distortion a little thus and again stagger.Wave-front corrector 24.1a or 24.2a of such optimization generates the wavefront of the ideal flat in the part beam participating in signal generation when nominal installation site.
Second wave-front corrector 24.1b or 24.2 also can optimize in a similar manner.For this reason, the propagation that returns that wavefront gets back to wave-front corrector 24.1b or 24.2b from detector cells by the radial calibration of metering device 10 or graduated disk 11 by means of the part beam of desired collimation is calculated, and makes the raster phase of wave-front corrector 24.1b or 24.2b again equal these wavefront.Computing method are from about known the pertinent literature of diffraction optical element as used herein.Calculate the radial scan structure again drawing distortion a little and dislocation more accurately.
Because flat wavefront is converted to flat wavefront by beam direction reverser 26.1,26.2 or the prism that arranges again for this reason, therefore wavefront correction does not disturb by it.Therefore, when through wave-front corrector 24.1b or 24.2b, wavefront, by predistortion, makes after second diffraction at metering device 10 place, for two part beams TSb1, TS2b, all produce smooth wavefront.
Therefore, by reflector element constructed according to the invention, the maximum interference constant of position signalling that the wavefront correction completely (nominal wavefront correction) and ensureing thus of the nominal installation site of all parts of position measurement apparatus generates and maximum signal can be ensured.As compared to from the wavefront correction utilizing spherical mirror and roof prism to carry out commonly known in the art, this is significant improvement.
, when metering device 10 or graduated disk offset with nominal installation site a little or tilt, wavefront itself can be corrected by reflector element to another important requirement of reflector element.At this, especially the radial direction of metering device 10 is crucial especially to produced signal quality with tangential skew.Recognize within the scope of the invention, can correct especially by the suitable beam direction reverser 26.1,26.2 of selection the wavefront distortion caused like this in reflector element.Therefore, the reverberator of the prism such as such as arranged in the present first embodiment and so on is suitable for as ideal beam direction reverser.The beam gradient determined by wavefront gradients of incident portion beam is transformed into the identical beam gradient of emission parts beam by this first embodiment.In this way, the additional wavefront distortion (wavefront correction caused by tolerance) occurred due to little alignment error correcting two interference portion beams.The interference constant significantly improved causes the signal caused by tolerance position signalling is medium and small to decline, otherwise or causes large location tolerance.Especially radial with tangential location tolerance with compared with solution commonly known in the art by so obvious expansion.At this, except the prism arranged in a first embodiment, can also arrange the alternative structure of beam direction reverser 26.1,26.2, this sets forth further by according to example below.
second embodiment
The scanning optical path of the second embodiment according to optical position measuring instrument of the present invention is schematically shown in Fig. 6,7a and 7b; At this, these accompanying drawings correspond to the scanning optical path figure of the first embodiment.The wave-front corrector of the second embodiment according to optical position measuring instrument of the present invention has been shown in Fig. 8.Below only by the key distinction between further investigated and the first example discussed in detail.
Therefore, first specify now: alternately construct the prism being configured to beam direction reverser in a first embodiment.Therefore in a second embodiment, beam direction reverser is configured to spherical mirror 226.1a, 226.2a respectively and is arranged in the combination of catoptron 226.1,226.2 at lens focus place.At this, in radiative process, being first upward through lens 226.1a, 226.2a in beam propagation side, is then catoptron 226.1,226.2, and is finally lens 226.1a, 226.2a again.
In addition, wave-front corrector 224.1a, 224.b, 224.2a, 224.2b of reflector element are not implemented to the diffraction optical element of surface sweeping raster mode, and are implemented as refraction optical element.In addition different from the first embodiment, these optical elements do not have for light path being orientated the central optical deflection parallel with optical axis OA.More precisely, remain in x-z plane from metering device 210 to the central beam direction of catoptron 226.1,226.2.
Show two wave-front correctors 224.1a, 224.1b of this embodiment with exemplary form in Fig. 8.At this, required wavefront correction is caused with the deflection of position about (locally) by little, this deflection is realized by the refraction of saddle type of the scanning board 223.1 with different surfaces gradient, and equals the diffraction optical element of the first embodiment or the deflection of raster.Along with the decline (increase of y value) of mirror position, become stronger to the tangential deflection in optical axis OA direction.
The Production Example of refraction wave-front corrector 224.1a, 224.1b is as undertaken by being impressed into by corresponding device in suitable former or by milling and detail sanding subsequently.In addition, also can by thermoforming rectangular glass rod be rotated into spirality and then dorsal part be polished and polish.
Except the parts of setting forth in the past, the second embodiment is consistent with the first embodiment in principle.
3rd embodiment
Illustrate in Fig. 9,10a and 10b and to have constructed according to the principle of the 3rd embodiment of optical position measuring instrument of the present invention.At this, this diagram illustrates corresponding to the scanning optical path of the first and second embodiments again.At this, these diagrams correspond to the scanning optical path of the first and second embodiments again.Only set forth the key distinction between embodiment up to now below.
The beam launched by the light source 321 being configured to laser diode is collimated optics 322 and collimates, and arrives graduated disk 311.Graduated disk 311 is furnished with metering device 310 again that be configured to radial calibration.So the part beam being deflected the+1/-1 order of diffraction is fallen on the first raster 324.1a or 324.2a, namely on diffraction optical element.
In this embodiment, raster 324.1a, 324.2a combine different optical functions, and that is, they are configured to diffraction combined optical element again.First, raster comprises wave front correcting function corresponding to the first embodiment and deflection respectively.Therefore, incident portion beam is deflected to parallel with optical axis OA by this raster, and the wavefront of part beam is corrected as and makes it first for smooth.Raster 324.1a, 324.2a additionally comprise optical lens function, by this optical lens function, part beam are focused on catoptron 326.1,326.2.At this, the position (X of respective lens focus
p1, Y
p1), (X
p1, Y
p1) draw according to lower relation of plane 3.1-3.3:
(equation 3.1)
(equation 3.2)
(equation 3.3).
Therefore, the optical function of the optical function of wave-front corrector with the lens element of the beam direction reverser in previous embodiment is combined by raster 324.1a, 324.2a.
In order to realize different optical functions in single diffraction optical element or raster, introducing should be superposed and often plant the different phase shift of optical element or optical function and make these phase shifts equal the phase bit function of corresponding diffraction optical element.So, this phase bit function or the directly given structure with the diffraction optical element that breaks of typical saw-toothed profile, or be quantized such as to describe binary or level Four diffraction optical element.At this, to be phase depth be again the binary phase grat structure of 180 ° of special low cost.
By raster 324.1a or 324.2a, part beam is focused onto catoptron 326.1 or 326.2, and arrives other raster 324.1b and 324.2b after reflection.This raster 324.1b and 324.2b is equally again containing multiple optical function.By being configured in optical lens function wherein, part beam is collimated first again, then being distorted to by the optical function of wave-front corrector and deflection makes part beam be collimated after the diffraction again at metering device 30 place, but becomes irradiation angle to propagate with optical axis OA.At this, the beam angle α produced is confirmed as two part beams are superposed at associating grating 327 place of scanning board 323 bottom side.Two part beams mix and in the produced the 0th and the+1/-1 order of diffraction, generate the part beam of phase shift by associating grating 327 in known manner, and the detector element 329.1-329.3 that described part beam is detected device unit detects.In this embodiment, do not need polarizing optic to generate phase shifted position signal.Therefore in this embodiment, detector cells only comprises detector element 329.1-329.3.The preferably phase shift of 120 ° of part beam can be realized by the brace width of the selected phase degree of depth suitably and associating grating 327, and this has such as given open in EP0163362B1.The grating constant of associating grating 327 is confirmed as making the part beam fallen on it be deflected to parallel with optical axis respectively by the diffraction in first order of diffraction.
Therefore, the beam direction reverser of this embodiment is by the optical lens function of raster 324.1a, 324.2a and catoptron 326.1,326.2.In radiative process, what beam propagation direction was each passed through is optical lens or raster 324.1a, 324.2a, catoptron 326.1,326.2, and then is optical lens or raster 324.1a, 324.2a.
the flexible program through changing of the 3rd embodiment
If the 3rd embodiment set forth before abandoning under the condition that part beam is parallel to optical axis in scanning board 323, then draw the flexible program through changing shown in Figure 11 a and 11b of the 3rd embodiment.
At this, the optical function of setting forth before raster 324.1a ', 324.2a ' and 324.1b ', 324.2b ' comprise.But the central optical deflection on the direction of measurement of raster 324.1a ', 324.2a ' is selected as less and raster 324.1b ', 324.2b ' are selected as comparatively large, still part beam is superposed again at associating grating 327 ' place.In this flexible program of optical position measuring instrument according to the present invention, part beam is parallel with optical axis OA in surface sweeping plate 323 ' as can be seen.
At the radiative process of light source 321 ' to the dislocation in y-direction of first diffraction at metering device 310 ' place and the later radiative process of second diffraction at metering device 310 ' place by selecting raster 324.1a ', 324.2a ' and 324.1b ', the y position of lens focus of optical lens function of 324.2b ' determines.The size of this dislocation of radiative process is at least chosen as the radiative process making the diffraction from light source 321 ' to metering device 310 ' and is not superposed at the radiative process that the diffraction at metering device 310 ' place is later.But the size of this dislocation can be selected as making to add radius R on metering device 310 '
athe unshowned additional calibration vestige at place.Such calibration vestige may be used for generating reference pulse signal, and this has such as given disclosing in the EP1923673A2 of inventor.
Calculating and first embodiment of the optical function of raster 324.1b ' or 324.2b ' are carried out similarly.The part beam collimated by collimated beam is from the detector element 329.1 '-329.3 of detector cells ' calculate the first wavefront distortion or phase shift to the propagation that returns of raster 324.1b ' or 324.2b '.By from focus to catoptron 326.1 ' or 326.2 ' forward direction calculate the second phase shift.So the difference of two phase shifts just in time corresponds to following phase place: this phase place will be introduced corresponding diffraction optical element and therefore be the phase bit function of this diffraction optical element.
Illustrate in Figure 12 according to surface sweeping grating 324.1a ', the 324.1b ' of this flexible program of optical position measuring instrument of the present invention and the structure that simplifies of the raster 324.2a ' of Mirror Symmetry, the height of 324.2b ' with it.
By the different optical function in combination Diffraction scans structure or raster, these embodiments according to optical position measuring instrument of the present invention closely and at low cost can be constructed.Because catoptron 326.1 ', 326.2 ' can be coated on scanning board 323 ' in addition one chip, therefore draw the structure to fluctuation and temperature-insensitive of simple, the robust of scanning element 320 '.
In order to reduce the wavefront distortion caused by tolerance further, advantageously verified, not equal by the focal length of the integrated lens be configured in the first and second raster 324.1a ', 324.2a ', 324.1b ' and 324.2b ', but be selected as slightly different.If f1 represents the focal length measured in scanning board medium of the first lens, f2 represents the respective focal of the second lens, then the combination of two lens is transformed into the part beam of collimation the part beam of collimation further, has been about to following formula and has set up:
(equation 4)
Wherein:
The focal length of f1:=first lens
The focal length of f2:=second lens
The sweep radius of the first scanning position on r1:=metering device
The sweep radius of the second scanning position on r2:=metering device
D
a: the thickness of=scanning board.
Particularly advantageously, according to lower relation of plane 5, the ratio f1/f2 of focal length is selected according to the correlation proportion of sweep radius r1 and r2 of first on metering device 310 and the second scanning position:
(equation 5).
So-called Kepler telescope is characterized by this condition, this Kepler telescope has negative imaging scale, and the scanning position of the first outside is projected to the scanning position (or alternately inner scanning position being projected to external scan position in the way to enlarge) of the second inside in the mode reduced.When little radial direction or the tangential skew of graduated disk 311, produce along with radius increases and the local wavefront inclination of reduction.This dependence is compensated by the relation according to equation 5, its mode be by the long-focus lens of external scan position before the larger beam direction that changes after the section focal length lenses translating into inner scanning position below of radiation direction change.This optimization can refinement further, its mode determines for each first scanning position (x in each scanning position, y) and distribute the second scanning position (x ', y ') meet the local lens focal distance f 1(x of equation 4, and f2(x ' y), y '), and in addition radial and tangential local beam direction change is transferred to the second scanning position from the first scanning position respectively by this way, makes the above-mentioned radial dependence of its optimally compensated wave top rake.Realize the location tolerance increased thus further.
4th embodiment
Illustrate in Figure 13 and Figure 14 a and 14b and to have constructed according to the principle of the 4th embodiment of optical position measuring instrument of the present invention.Described diagram corresponds to the scanning optical path figure of previous embodiment.Then again the main difference with embodiment up to now is only set forth.
In the 4th embodiment of optical position measuring instrument according to the present invention, divergent light source irradiates the metering device 410 on graduated disk 411 now.At this, use so-called VCSEL light source (VerticalCavitySurfaceEmittingLaser(vertical cavity surface emitting laser) preferably as light source).Therefore, collimating optics is not set.
At metering device 410 place, diffracted or beam splitting is the+1/-1 order of diffraction to divergent beam.At this, the first raster 424.1a, 424.2a combine multiple optical function again.Therefore, function is constructed as follows by it: for the optical function of lens collimated divergent portion beam; For the optical function of the wavefront correction of wavefront distortion, this function is realized by the metering device 410 being configured to radial calibration on graduated disk 411; And part beam is focused on the optical function of condenser lens of center of upside of scanning board 424.At part beam after the reflection at catoptron 426 place, part beam arrives the second raster 424.1b, 424.2b, and described second raster has multiple optical function equally.Therefore, second raster 424.1b, 424.2b collimate the part beam dispersed, and these part beams experience is for the wavefront correction of the diffraction subsequently at metering device 410 or radial calibration place, and part beam focuses on the detector element 429.1-429.3 of detector cells.Finally, combining grating 427 makes two part beams interfere.
The feature of this embodiment is the diameter scans of the metering device 410 on graduated disk 411.Thus graduated disk 411 at x-y plane bias internal time reduce possible measuring error.In this embodiment, ideal beam direction reverser is retroreflector, and this retroreflector is made up of the optical lens function of raster 424.1a, 424.2a, 424.1b, 424.2b and catoptron 426 as in the third embodiment.In radiative process, again by optical lens or raster 424.1a, 424.2a, catoptron 426, and and then through lens or raster 424.1b, 424.2b.
According to the embodiment set forth above, optical position measuring instrument according to the present invention divides the radial calibration of scanning having and comprise as metering device, in these embodiments, exists a series ofly different realize possibility for the reflector element in scanning element.But by all different optical functions realizing possibility and ensure below reflector element.
Little radial direction (tangentially) beam direction of-incident portion beam changes substantially contrary radial direction (tangentially) beam direction being converted into emission parts beam respectively and changes.
Little radial direction (tangentially) beam spot of-incident portion beam changes substantially contrary radial direction (tangentially) beam spot being converted into emission parts beam respectively and changes.
-the wavefront distortion that produces due to the diffraction at radial calibration place is converted into the wavelength distortion that the wavefront distortion that causes second diffraction at radial calibration place compensates.
5th embodiment
Below, the different flexible programs according to the 5th embodiment of optical position measuring instrument of the present invention are described now.These flexible programs are substantially with the difference of example set forth up to now, and scanning metering device is configured to the cylinder calibration on the periphery of rotary index cylinder.At this, turning axle overlaps with the major axis of index sleeve.
The structure of the first and second flexible programs of the 5th embodiment is schematically shown in Figure 15 and 16.The difference of these two flexible programs is, according in the flexible program of Figure 15, the direction of measurement of scanning is oriented to tangential x, and according in the flexible program of Figure 16, the direction of measurement of scanning is oriented to radial y.This means, by according to Figure 15 according to optical position measuring instrument of the present invention, the position angle of rotary index cylinder 510 can be determined, and by according to the flexible program of Figure 16, the radial deflection of rotary index cylinder 510 ' can be determined.
Scanning in these two flexible programs in 5th embodiment especially corresponds to the scanning of setting forth in previous embodiment in principle in the first reflector element that there is the first and second wave-front correctors and beam direction reverser.Therefore, several aspects of being worth mentioning of these flexible programs are only briefly inquired into below.
The beam be collimated by collimating optical system 522,522 ' arrives index sleeve 510,510 ', and the periphery of these index sleeves is furnished with a metering device of calibration form 511,511 '.At this, the metering device 511 in Figure 15 has the calibration grid stroke in radial direction, when metering device 511 ' in figure 16, calibration grid stroke be disposed in tangential on.To be deflected to or beam splitting is that the part beam of+1/-1 order of diffraction experiences the distortion of its corresponding wavefront due to the reflection at bending cylinder calibration place.
In addition, according in the flexible program of Figure 16, the collimated beam fallen on metering device 511 ' does not meet with its summit.At this, the order of diffraction reflected from metering device 510 ' or part beam additionally experience the gradient the x direction vertical with direction of measurement.
Diffraction optical element or raster 524.1a, 524.2a or 524.1a ', 524.2a ' are by these wavefront distortion of phase place function compensation of its corresponding selection, and compensate the beam gradient produced in the case of figure 16, and part beam is focused on catoptron 526.1,526.2 or 526.1 ', 526.2 '.Therefrom, the part beam dispersed arrives raster 524.1b, 524.2b, 524.1b of being configured to diffraction optical element equally ', 524.2b '.At this, their phase bit function except respective symbol with the first raster 524.1a, 524.2a, 524.1a ', the phase bit function of 524.2a ' is equal.At metering device 511 or 511 ' place is again after secondary reflection, and two part beams again have smooth wavefront and then interfere with each other.Raster 524.1a, 524.2a or 524.1a ', 524.2a ' combine the optical function of wave-front corrector, lens and beam deflection again.
The lens function constructed in raster 524.1a, 524.2a or 524.1a ', 524.2a ' can be configured to spherical lens function as in second, third and the 4th embodiment.But in scanning according to the index sleeve 510,510 ' of Figure 15 and 16, substantially only on tangential, there is wavefront distortion.Diametrically, index sleeve 510,510 ' is rectilinear, and metering device 511,511 ' or the deflecting action of cylinder calibration be constant.This can reach a conclusion, and not necessarily needs retroeflection axially.But this should it is contemplated that, in any case all need the retroeflection perpendicular to direction of measurement, to reduce the known tilt sensitive degree (" ripple inclination ") of scanning optics around optical axis OA.In this case, can consult clearly apply for into DE102005029917A1.Therefore, can abandon in the scanning of the index sleeve 510 ' only in the flexible program of Figure 16 with the complete retroeflection of direction of measurement.In all other circumstances, comprise the scanning of radial calibration, need the beam direction reverser with complete retroeflection.Complete retroeflection as described above can by prism, triple spiegel, spherical mirror with the combination of catoptron and by roof prism and the combination of cylindrical mirror with the lensing parallel with ridge seamed edge.And for non-fully, single shaft retroeflection, or need roof prism, or need the combination of cylindrical mirror and catoptron.According to the orientation of the single shaft retroeflection in the flexible program of Figure 16 must carry out make the ridge seamed edge of roof prism be oriented to axis or focus of cylindrical mirror on tangential.
As in the above-described first embodiment, according to the generation all carrying out phase shifted position signal in two flexible programs of Figure 15 and 16 in the mode of polarization optics.But equally also can with the 3rd embodiment similarly by having by the scanning optical path of combining grating of suitable constructions to obtain phase shifted position signal at this.
Corresponding measurement task may need if desired detect index sleeve 510 or 510 ' axial dipole field and position angle.In this case it is possible that merged by metering device 511 and 511 ', and be configured to the Cross grating calibration on the periphery of index sleeve.Reduce required installing space and the inertia torque of index sleeve thus.In addition, can in this case by using from that time six scanning elements altogether to determine the complete sextuple position of index sleeve.
The flexible program of the 5th embodiment according to optical position measuring instrument of the present invention is partially illustrated in Figure 17; The particular geometric size that Figure 18 is used for setting forth below this flexible program determines rule.The second flexible program of unshowned Cross grating calibration can be had as previously outlined like that for detecting a calibration 610 or 510 according to this flexible program of optical position measuring instrument of the present invention ' axial dipole field and position angle or determined the sextuple position of index sleeve 611 by six scanning elements 620.Use following scanning: the normal to a surface of direction of measurement around cylinder periphery of this scanning rotates for this reason.This, by carrying out orientation to realize to the calibration bar of metering device 610, makes this metering device be arranged to equally and rotates around described surface normal.At this, the symmetry of the +/-45o of two direction of measurement of Cross grating calibration is rotated advantageously, need not manufacture the two not identical scanning element with different diffraction optical element in scanning board.More precisely, then can use identical but each other around the scanning element that described normal direction is rotated.
When constructing metering device like this, because the side of the incidence point of sweep test beam misplaces, when relative to scanning board vertical irradiation, two first order part beams be reflected back from metering device are fallen scanning board symmetrically.Therefore, two the first raster 624.1a, 624.2a that especially should correct wavefront distortion be through are not identical after mirror-reflection equally.Therefore, nonideal installation or at the wavelength departure of light source in when designing during wavelength as prerequisite, the wavefront of two part beams interfered with each other very differently is out of shape.Therefore, this will cause the rapid reduction of modulating stage and cause the signal magnitude of generated position signalling to reduce rapidly thus.
This symmetry of first diffraction optical element 624.1a and 624.2a and the location tolerance of reduction be associated with it can by irradiating the oblique incidence of beam S and being cancelled by the incidence of the same inclination of the second part beam TS interfered with each other, and this has given explanation in the top of Figure 17 and Figure 18.
This realizes approx in the following way: through the breakthrough point of scanning board 623 and the incident angle ε of irradiation beam S
bbe selected as making the 0th of the part beam be reflected back from metering device 610 or cylinder calibration the grade vertically and Central places fall between two the first raster 624.1a and 624.2a.This is illustrated in figure 18.
Therefore, the incident angle ε of beam S is irradiated
bpreferably select according to following formula:
(equation 6)
Wherein:
X
0the scanning position in the x direction of :=when first diffraction at metering device place
The radius of R:=index sleeve.
Following formula is had to set up approx for large cylinder gradient R:
(equation 6.1).
The x coordinate of illumination radiation S through the breakthrough point of scanning board 623 bottom side is drawn by following formula:
(equation 7)
Wherein:
D
l: the sweep spacing between the summit of=cylinder calibration and scanning board
Following formula is had to set up approx for large cylinder gradient R:
(equation 7.1).
According to following formula, illumination radiation S passes the mean value of y coordinate corresponding to the y coordinate of the first raster 624.1a and 624.2a of the breakthrough point of scanning board 623 bottom side:
(equation 8).
Show that the corresponding geometric parameter (emergence angle of beam TS is interfered in outgoing according to following formula; Penetrate coordinate):
(equation 9.1)
(equation 9.2)
(equation 9.3).
Use oblique illumination for direction of measurement not for tangential or radial all scanning are all useful.Therefore, so raster 624.1a, 624.2a and 624.1b, the 624.2b of symmetric construction can be arranged; In addition, the large tolerance in the nominal position relating to index sleeve can be used.At this meaningfully, select the first and second analyzing spots on metering device 610 or index sleeve symmetrical about cylinder summit in the x direction.This causes wave-front corrector to correct bending the wavefront be bent due to cylinder, and wherein the oblique illumination that is tilted through of wavefront is compensated.
As in first embodiment with radial grating scanning, cylinder scanning is shown: retroreflector is the ideal solution of beam direction reverser.This can be owing to, and when index sleeve deviates from its nominal position, occur the wavefront distortion caused by tolerance, this wavefront distortion is substantially wavetilt and is beam gradient thus.By retroeflection, these beam gradients are cancelled at this and cause the optimum of two part beams to be interfered.
6th embodiment
Finally according to Figure 19,20a and 20b, the 6th embodiment according to optical position measuring instrument of the present invention is described.
All the time specify in embodiment set forth up to now: metering device, two wave-front correctors and beam direction reverser are passed by beam or part beam in the following sequence on beam propagation direction:
Metering device (the first diffraction) the-the first wave-front corrector-beam direction reverser the-the second wave-front corrector-metering device (the second diffraction).
According to this order by different arrangements of elements in optical position measuring instrument according to the present invention.
But within the scope of the invention also possible that, these elements also can be passed by beam or part beam in the following sequence:
First wave-front corrector-metering device (the first diffraction)-beam direction reverser-metering device (the second diffraction) the-the second wave-front corrector.
Therefore generally can think, according to the present invention, reflector element in scanning element is arranged and/or is constructed so that before beam finally arrives detector cells, first beam combines through first of metering device and the first wave-front corrector, then carry out the past back reflective of part beam in metering device direction by beam direction reverser, and then part beam combines through second of metering device and the second wave-front corrector.
The embodiment of optical position measuring instrument has been shown in Figure 19,20a and 20b, and what wherein beam was mentioned with second time passes through different elements.
The beam launched from light source 621 is collimated by collimating optical system 622, and arrives the first raster 624a, and this first raster is arranged on scanning board 623.By the first raster 624a, Incident beams is the diffracted portion beam of two+1/-1 orders of diffraction by beam splitting.Then, two part beams are fallen on the metering device 610 being configured to radial calibration on graduated disk 611.There, part beam is again diffracted to+1/-1 the order of diffraction and is reflected back toward with substantially contrary with incident direction direction of measurement x as found out from Figure 20 a.Then, the part beam be reflected back is fallen and is configured on the beam direction reverser of prism, from this beam direction reverser, this part beam again with the direction of metering device 610 by retroeflection.At part beam again after metering device 610, described part beam arrives the second raster 624b again, and this second raster 624b is by two part beam superpositions and interfere.As in the 3rd embodiment above, second raster is constructed to the beam making preferably to send single phase shift each other 120 ° of phase shift in the produced the 0th and the+1/-1 order of diffraction, and described beam is detected by the detector element 629.1-629.3 of detector cells.
First raster 624a combines different optical function again.Therefore, the first raster is served as the beam beam splitting from light source 621 incidence is the beam-splitting optical grating of two part beams.Utilize this beam splitting, contact the deflection of the symmetry to two part beams simultaneously.In addition, the first beam-splitting optical grating 624a serves as the first wave-front corrector.Thus, the emerging wavefront of two part beams is distorted to the part beam making to there is collimation respectively after the diffraction at metering device 610 place being configured to radial calibration, and described part beam arrives the beam direction reverser being configured to prism.Therefore ensure again, utilize the wavefront of the part beam participated in carry out retroeflection.
With it similarly, the second raster 624b also combines different optical functions.Therefore, the second surface sweeping grating 624 serves as the second wave-front corrector, and the second diffraction due to metering device place is transformed into smooth wavefront by the wavefront of the part beam of distortion by this wave-front corrector again.In addition, in this embodiment, the second raster 624b also serves as associating grating, and this associating grating makes two part beams interfere and convert thereof into three outgoing phase shift beams.
From describe up to now different according to the embodiment of optical position measuring instrument of the present invention, distribute undivided raster to the part beam of two beam splitting at this.Therefore need in this embodiment to correct in its corresponding wavefront respectively two part beams.For this reason, the first and second raster 624a, 624b are configured to diffraction structure.
Special advantage as the 6th embodiment of optical position measuring instrument according to the present invention finally it should be mentioned that this embodiment has structural form compact especially.
Certainly, except the different embodiments elaborated up to now of optical position measuring instrument according to the present invention, other operational feasibility is produced within the scope of the invention.Briefly introduce various flexible program below.
If the position of orientation of such as the first scanning position deviates from the nominal value of the second scanning position position of orientation of radial calibration when scanning radial calibration, then the wavefront gradients of two scanning positions is no longer aligned when graduated disk offsets out nominal position.More precisely, described wavefront gradients is rotated and the change of its value each other.Therefore, additional optical devices are introduced, as prism (such as many husbands (Dove) prism) or lens device, correspondingly to transmit these wavefront gradients, namely to ensure optimum image rotation and convergent-divergent.
Be alternative in and use pure refraction or the wave-front corrector of pure diffraction and lens, also can use refraction and the diffraction element of mixing.In addition, also can use the mirror optics of suitable constructions for this reason.
Certainly, the metering device of scanning can alternately construct equally, is namely configured to printing opacity metering device.
Other heterogeneous indexing structure can be also may be used for except the scanning of radial or cylinder calibration according to sweeping scheme of the present invention.
It is additionally possible that beam direction reverser is only configured to prism, triple spiegel or there are the lens of mirror.Also can use the combination of 90 ° of ridges and cylindrical mirror, being wherein oriented to and roof prism parallel with ridge seamed edge and must being disposed in the focal plane of lens etc. of lensing for this reason.
Claims (16)
1. for detecting scanning element (20; 220; 320; 420; 520; 520 '; 620; 2000) and metering device (10; 210; 310; 410; 510; 510 '; 610; 1000) optical position measuring instrument of relative position, wherein scanning element (20; 220; 320; 420; 520; 520 '; 620; 2000) and metering device (10; 210; 310; 410; 510; 510 '; 610; 1000) can move relative to each other along bending direction of measurement, and wherein
-scanning element (20; 220; 320; 420; 520; 520 '; 620; 2000) there is at least one reflector element (2000) and detector cells, and reflector element (2000) is made up of the first wave-front corrector (2100), beam direction reverser (2300) and the second wave-front corrector (2200); And
-reflector element (2000) is in scanning element (20; 220; 320; 420; 520; 520 '; 620; 2000) be arranged in and/or be constructed so that before part beam then arrives detector cells, first beam passes by metering device (10; 210; 310; 410; 510; 510 '; 610; 1000) the first combination that and the first wave-front corrector (2100) is formed, then carries out part beam at metering device (10 by beam direction reverser (2300); 210; 310; 410; 510; 510 '; 610) return reflection on direction, and part beam is then through by metering device (10; 210; 310; 410; 510; 510 '; 610; 1000) the second combination that and the second wave-front corrector (2200) is formed, wherein
-ensured, by metering device (10 by reflector element (2000); 210; 310; 410; 510; 510 '; 610; 1000) wavefront distortion of the part beam of the first diffraction generation at place is converted into following wavefront distortion, and described wavefront distortion compensates at metering device (10; 210; 310; 410; 510; 510 '; 610) wavefront distortion of the part beam produced when the second diffraction occurs at place.
2. optical position measuring instrument according to claim 1, wherein
-will from metering device (10 by the first wave-front corrector (2100); 210; 310; 410; 510; 510 '; 610) wave-front conversion of the first combination outgoing of with the first wave-front corrector (2100) becomes to have the collimating part beam of flat wavefront; And
-will from metering device (10 by the second wave-front corrector (2200); 210; 310; 410; 510; 510 '; 610) wave-front conversion of the second combination outgoing of with the second wave-front corrector (2200) becomes to have the collimating part beam of flat wavefront, makes the wavefront of the part beam that superposition occurs at metering device (10; 210; 310; 410; 510; 510 '; 610) second diffraction at place is later identical at superposed positions place.
3. optical position measuring instrument according to claim 1 and 2, wherein
-metering device (10; 210; 310; 410; 510; 510 '; 610) the first combination of and the first wave-front corrector (2100) is with metering device (10; 210; 310; 410; 510; 510 '; 610) order of the-the first wave-front corrector (2100) is disposed on beam propagation direction; And
-metering device (10; 210; 310; 410; 510; 510 '; 610; 1000) the second combination of and the second wave-front corrector (2200) is with the second wave-front corrector (2200)-metering device (10; 210; 310; 410; 510; 510 '; 610; 1000) order is disposed on beam propagation direction.
4. optical position measuring instrument according to claim 1 and 2, wherein
-metering device (10; 210; 310; 410; 510; 510 '; 610) the first combination of and the first wave-front corrector (2100) is with the first wave-front corrector (2100)-metering device (10; 210; 310; 410; 510; 510 '; 610) order is disposed on beam propagation direction; And
-metering device (10; 210; 310; 410; 510; 510 '; 610) the second combination of and the second wave-front corrector (2200) is with metering device (10; 210; 310; 410; 510; 510 '; 610) order of the-the second wave-front corrector (2200) is disposed on beam propagation direction.
5. optical position measuring instrument according to claim 1, wherein beam direction reverser (2300) is constructed to make to reverse the beam direction of the part beam reflected from this beam direction reverser to carry out in 2 orthogonal directions.
6. optical position measuring instrument according to claim 1, wherein beam direction reverser (2300) is configured to triple spiegel or prism.
7. optical position measuring instrument according to claim 1, wherein beam direction reverser (2300) is configured to the combination of lens and catoptron.
8. optical position measuring instrument according to claim 7, wherein wave-front corrector (2100; 2200) and/or the lens of beam direction reverser (2300) be configured to refraction optical element.
9. optical position measuring instrument according to claim 6, wherein wave-front corrector (2100; 2200) diffraction optical element is configured to.
10. optical position measuring instrument according to claim 7, wherein wave-front corrector (2100; 2200) diffraction optical element is configured to.
11. optical position measuring instruments according to claim 9, wherein wave-front corrector (2100; 2200) and the lens of beam direction reverser (2300) be configured to diffraction optical element.
12. optical position measuring instruments according to claim 9, wherein wave-front corrector (2100; 2200) be configured to the diffraction optics composition element of raster form respectively, these raster in addition to the part beam fallen on it have in following Additional optical function one of at least:
The effect of-deflection optical
-optical beam splitting or synergy
-to the optical focus effect on catoptron.
13.-12 one of at least described optical position measuring instruments according to Claim 8, wherein catoptron and diffraction optical element are disposed in transparent scanning board (23; 223; 323; 423; 523; 523 '; 623) opposite side.
14. optical position measuring instruments according to claim 1, wherein metering device (10; 210; 310; 410) graduated disk (11 rotated around turning axle is configured to; 211; 311; 411) the radial calibration on and be arranged as concentric around turning axle.
15. optical position measuring instruments according to claim 1, wherein metering device (510; 510 '; 610) rotary index cylinder (511 is configured to; 511 '; 611) the cylinder calibration on periphery, wherein turning axle overlaps with the major axis of index sleeve.
16. optical position measuring instruments according to claim 15, the optical element wherein in scanning element in (620) is constructed and is arranged so that the beam launched from light source is fallen a calibration with the angle being not equal to 90 °.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102010029211A DE102010029211A1 (en) | 2010-05-21 | 2010-05-21 | Optical position measuring device |
| DE102010029211.7 | 2010-05-21 |
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| Publication Number | Publication Date |
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| CN102288113A CN102288113A (en) | 2011-12-21 |
| CN102288113B true CN102288113B (en) | 2016-04-06 |
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| CN201110131850.1A Active CN102288113B (en) | 2010-05-21 | 2011-05-20 | Optical position measuring instrument |
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| US (1) | US9766098B2 (en) |
| EP (1) | EP2388558B1 (en) |
| JP (1) | JP6026084B2 (en) |
| CN (1) | CN102288113B (en) |
| DE (1) | DE102010029211A1 (en) |
| ES (1) | ES2699694T3 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102011081879A1 (en) | 2010-11-03 | 2012-05-03 | Dr. Johannes Heidenhain Gmbh | Optical angle measuring device |
| DE102011082570A1 (en) * | 2011-09-13 | 2013-03-14 | Dr. Johannes Heidenhain Gmbh | Rotary position measuring device |
| DE102012210309A1 (en) * | 2012-06-19 | 2013-12-19 | Dr. Johannes Heidenhain Gmbh | Position measuring device |
| DE102013206693A1 (en) * | 2013-04-15 | 2014-10-16 | Dr. Johannes Heidenhain Gmbh | Device for interferential distance measurement |
| DE102013210999A1 (en) * | 2013-06-13 | 2014-12-18 | Dr. Johannes Heidenhain Gmbh | measuring device |
| DE102013221898A1 (en) * | 2013-10-29 | 2015-04-30 | Dr. Johannes Heidenhain Gmbh | Device for determining position |
| DE102015209117A1 (en) * | 2014-06-05 | 2015-12-10 | Dr. Johannes Heidenhain Gmbh | Interferential position measuring device and method for operating an interferential position measuring device |
| DE102014211004A1 (en) | 2014-06-10 | 2015-12-17 | Dr. Johannes Heidenhain Gmbh | Optical position measuring device |
| DE102015203188A1 (en) * | 2015-02-23 | 2016-08-25 | Dr. Johannes Heidenhain Gmbh | Optical position measuring device |
| JP6702666B2 (en) * | 2015-07-28 | 2020-06-03 | 株式会社ミツトヨ | Displacement detection device |
| KR20180132921A (en) * | 2016-04-21 | 2018-12-12 | 몰레큘라 비스타 인크. | Optical Shift Correction System and Method |
| DE102017205504A1 (en) * | 2017-03-31 | 2018-10-04 | Robert Bosch Gmbh | Optical scanning system |
| DE102017205623A1 (en) * | 2017-04-03 | 2018-10-04 | Robert Bosch Gmbh | LIDAR device and method for scanning a scan angle |
| DE102019206937A1 (en) * | 2019-05-14 | 2020-11-19 | Dr. Johannes Heidenhain Gmbh | Optical position measuring device |
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|---|---|---|---|---|
| US5442172A (en) * | 1994-05-27 | 1995-08-15 | International Business Machines Corporation | Wavefront reconstruction optics for use in a disk drive position measurement system |
| CN101144730A (en) * | 2006-09-12 | 2008-03-19 | 约翰尼斯海登海恩博士股份有限公司 | Position measuring device |
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| GB8413955D0 (en) | 1984-05-31 | 1984-07-04 | Pa Consulting Services | Displacement measuring apparatus |
| DE3905730C2 (en) | 1989-02-24 | 1995-06-14 | Heidenhain Gmbh Dr Johannes | Position measuring device |
| US5079418A (en) | 1990-02-20 | 1992-01-07 | Dr. Johannes Heidenhain Gmbh | Position measuring apparatus with reflection |
| JP2862417B2 (en) * | 1990-11-16 | 1999-03-03 | キヤノン株式会社 | Displacement measuring device and method |
| JP4846909B2 (en) * | 2000-02-15 | 2011-12-28 | キヤノン株式会社 | Optical encoder and diffraction grating displacement measuring method |
| DE102004035172A1 (en) * | 2004-07-16 | 2006-02-09 | Dr. Johannes Heidenhain Gmbh | Position measuring device |
| DE102005029917A1 (en) | 2005-06-28 | 2007-01-04 | Dr. Johannes Heidenhain Gmbh | Position measuring device |
| JP5147368B2 (en) * | 2006-11-20 | 2013-02-20 | ドクトル・ヨハネス・ハイデンハイン・ゲゼルシヤフト・ミツト・ベシユレンクテル・ハフツング | Encoder |
| DE102007035345A1 (en) | 2006-11-20 | 2008-05-21 | Dr. Johannes Heidenhain Gmbh | Position measuring device |
-
2010
- 2010-05-21 DE DE102010029211A patent/DE102010029211A1/en not_active Withdrawn
-
2011
- 2011-05-04 EP EP11164731.9A patent/EP2388558B1/en active Active
- 2011-05-04 ES ES11164731T patent/ES2699694T3/en active Active
- 2011-05-13 JP JP2011107788A patent/JP6026084B2/en active Active
- 2011-05-16 US US13/068,659 patent/US9766098B2/en active Active
- 2011-05-20 CN CN201110131850.1A patent/CN102288113B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5442172A (en) * | 1994-05-27 | 1995-08-15 | International Business Machines Corporation | Wavefront reconstruction optics for use in a disk drive position measurement system |
| CN101144730A (en) * | 2006-09-12 | 2008-03-19 | 约翰尼斯海登海恩博士股份有限公司 | Position measuring device |
Also Published As
| Publication number | Publication date |
|---|---|
| JP6026084B2 (en) | 2016-11-16 |
| ES2699694T3 (en) | 2019-02-12 |
| US20110286004A1 (en) | 2011-11-24 |
| DE102010029211A1 (en) | 2011-11-24 |
| CN102288113A (en) | 2011-12-21 |
| EP2388558B1 (en) | 2018-08-29 |
| US9766098B2 (en) | 2017-09-19 |
| JP2011247886A (en) | 2011-12-08 |
| EP2388558A2 (en) | 2011-11-23 |
| EP2388558A3 (en) | 2017-04-26 |
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